1. Technical Field
This disclosure relates to a sheet folding device configured to perform a folding process on a printed paper sheet (hereinafter, simply referred to as “sheet”) printed in a printing unit in an image forming device, by using a pair of folding rollers arranged on a sheet transfer path downstream of the printing unit.
2. Related Art
In Japanese Patent Application Publication No. 2002-193544, a sheet folding device equipped with a sheet folding technique is used in a case of making a sealed letter or the like by folding a printed sheet which is printed in a printing unit in an image forming device.
In the above sheet folding device, though illustration is omitted here, a printed sheet which is printed in an image forming unit in the image forming device is transferred into a Z-folding process unit, for example.
In this Z-folding process unit, first to third folding rollers are each provided with three large-diameter portions at a sheet transfer center portion and sheet transfer end portions, and a small-diameter portion is provided between the sheet transfer center portion and each sheet transfer end portion.
A Z-folding process is performed by transferring a printed sheet between the first to third folding rollers with the sheet brought into contact with only the large-diameter portions provided at the sheet transfer center portions of the first to third folding rollers while both end sides of the sheet are left out of contact with the first to third folding rollers.
In this way, the area of contact of the sheet with the first to third folding rollers is reduced, thus making it possible to ensure paths to relieve sheet folding pressure on the sheet upon application of the pressure. Accordingly, formation of creases on the sheet is prevented.